Telephone-exchange system.



C. L. GOODRUM.

TELEPHONE EXCHANGE SYSTEM..

APPLICATION FILED JUNE 29 1916:

Patented J uly 3, 1917.

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UNITED STATES PATENT OFFICE.

CHARLES L. GOODRUM, OF NEW YORK. N. Y.. ASSIGNOR TO WESTERN ELECTRIC COM- PANY INCORPORATED. OF NEW YORK, N. Y.,

A. CORPORATION OF NEW YORK- TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented July 3, 1917.

Application filed J one 29, 1916. Serial No. 1Q6,696.

To all whom it may concern:

Be it known that I. CHARLES L. GOODRUM, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Telephone- Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone eX-' change systems in which machine switching is used and more particularly to systems in which a calling subscribers line is extended to a trunk by the action of a line switch.

The object of this invention is to provide means for increasing the number of calls which may be handled by a line switch and to cause it to operate with greater accuracy.

A feature of this invention is the dividing of the group of lines served by a line switch into sub-groups each sub-group having master switch mec anism.

A further feature of the invention is the assigning of preferred trunks to each sub group, the multiples of these preferred trunks being slipped in groups to the contact banks of the other sub-groups.

An additional feature of the invention is an arrangement by which the subscribers in each sub-group have access to a plurality of trunks, and by which the sub-group master switch mechanism will release and return to position before one of the preferred trunks of such sub-group as soon as one of said preferred trunks becomes idle.

The switch structure in the embodiment of the invention shown is substantially similar to that shown in U. S. Patent No. 1,151,543, issued to A. E. Keith. In the present arrangement, the master switch is advanced step-by-step through its arc of movement and is returned to normal under spring tension when a holding pawl is withdrawn. It is obvious, however, that the invention is capable of application to a variety of line switch structures.

It is thought that the invention will be best understood from the following detailed description, reference being had to the accompanying drawing.

In the drawings, Figure 1 shows the substation circuits of a calling subscriber to the left of the dotted line. The circuits of the master switch mechanism of one sub-group are shown complete, while the circuits of the master switch mechanism of another subgroup are indicated at the right of the drawing. Fig. 2 shows schematically, the mechanical arrangement of the master switch mechanism and connecting plungers.

In the arrangement shown, the IOU-line group served by the switch is divided into five sub-groups, each group having master switch mechanism. To each sub-group are assigned two preferred trunks, the test terminals of these preferred trunks being slipped through the master contact banks of the sub-group mechanisms two by two, as indicated by the connections shown in the drawing between the sub-groups there represented.

Referring now to Fig. 2, the arrangement of the master switch mechanism will be briefly described. A shaft 31 carries at its upper end a ratchet wheel 32 arranged to be rotated step by step against the tension of a spiral spring 34. by means of a pawl 33 normally out of engagement with said ratchet wheel and operated by a magnet 17. A pair of master switch wipers 18 and 19 are secured to shaft 31 and rotate therewith over the master bank of contacts indicated at 36. Upon leaving their normal position, the wipers 18 and 19 allow an oif-normal contact 30 to be closed. A holding pawl 37 prevents return movement of the wipers during the energization of a holding, magnet 22. When magnet 22 is deenergized, the pawl 37 is disengaged by means of a spring (not shown), and the master switch is restored to normal. A U-shaped member 38 is rotated upon actuation of shaft 31, and plungers 7 are rotated therewith by the engagement of notches 39 in such plungers with a flange 40 on the member 38. Upon the energization of one of the line magnets 6, a plunger 7 will be operated to engage a set of trunk terminals indicated at 41, and will not be further rotated upon subsequent movement of member 38, since notch 39 is now out of engagement with flange 40. Upon deenergization of its associated mag- V net 6, an operated plunger 7 is returned to its normal position, and upon return movement of the member 38, will be engaged by such member and rotated therewith.

In Fig. 1 the magnet 6 and plunger 7 are not shown as operating in exactly the same manner as shown in Fig. 2. It is to be understood, however, that the method of representation in Fig.1 is merely to indicate that the energization of magnet 6 will operate plunger 7 to establish connection between the line and trunk contacts.

The circuits of the master switch mecha-.- nism of sub-group I are indicated to the left of the dotted line, while those of sub-floup II are partially indicated to the rig t of the dotted line.

The subscriber at substation A, desmng a connection, removes his receiver from the I switchhook, whereupon line relay 1 is enerarmature and the winding of relay 2 gized over a circuit from grounded battery, back contact of slow release relay 2, conductors 3 and 4, left-hand winding of relay 1, outer armature and back contact of cut-ofi relay 5, over the hue loop of the calling subscriber, inner armature and back contact of relay 5, and right-hand winding of relay 1 to ground. The lme relay, 1n pulling up, closes a circuit from grounde battery, left-hand winding of plunger operating magnet 6, and armature and front contact of relay 1 to groun Magnet 6 actuates a plunger 7 to close contacts 8, 9 and 10, to extend the subscribers line to a first selector. As soon as the plunger has established connection, a circuit is completed from grounded battery, right-hand winding of magnet 6, winding of cut-ofi relay 5, conductor 11, contact 8, trunk conductor 12 to ground. Relay 5 is energized and removes the control of the line relay from the calling subscriber in the well-known manner.

At the same time, relay 13 is energized over a circuit from grounded battery, winding of relay 13, conductor 14, contact 10 to ground. Relay 13, in operating, closes a 011'- cuit from grounded battery, inner armature and front contact of relay 13, conductor 15, master switch brush 19 and contact 16, conductor 14 and contact 10 to ground. In parallel with reay 2, stepping ma et 17 is energized from conductor 15, windm of stepping magnet 17, its armature and ack contact, to ground through master switch contact 16. The operation of magnet 17 causes the master switch mechanism to advance the line plungers and master switch brushes 18 and 19 one step to position before the terminals of the next trunk. The stepping magnet 17 interrupts its own circuit an if this second trunk is idle, the apparatus will come to rest in this position.

The windin of relays 2 and 17 are so proportioned t at during all times that the stepping magnet 17 is energized, the relay 2 is also energized. The function of relay 2 is to hold open the circuits of the line relays of its sub-group at all times during which the master switch mechanism of such subgroup is operating. Assuming now that the second trunk is busy, the stepping magnet will receive ground from test contact 20 and advance the plungers to position before the mechanism is under spring tension. As long as either of the trunk relays 13 and 21 is energized, magnet 22 is energized over a circuit from grounded battery, left-hand winding of magnet 22, conductor 23, to ground at the outer armature and front contact of either relay 13 or relay 21.

If, while the master mechanism is positloned before the third trunk, this trunk should be seized by a plunger in some other subgroup, the stepping magnet 17 would again be actuated by ground on test contact 24 in the well-known manner. The operation of the master switch mechanism after leaving the first .two trunks is unnecessary of further description until one of the preferred trunks becomes idle.

When one of the preferred trunks becomes idle, a circuit is closed from grounded battery through the right-hand winding of magnet 22, brush 18, segment 25, conductor 26, and either conductor 27 or conductor 28 to ground at the outer armature and back contact of either relay 21 or relay 13, accordmg to which relay has been denergized by removal of ground from the test contact of its trunk. Both windings of magnet 22 now being energized, the magnetic efiect of these windings is difierential and the holding pawl is relased, whereupon the master switch restored to normal position. The master switch mechanism now moves to position before the terminal sets of an idle trunk in a manner previously described.

If the relays 13 and 21 should fall off at exactly the same instant, the energizing circuit of the left-hand winding of magnet 22 is maintained over a circuit from grounded battery, left-hand windin of mag net 22, conductors 23 and 29, 0 -normal contact 30, armature and back contact of relay 21, and armature and back contact of relay 13 to ground.

' group II by conductor 31. It will e noted that in group II this tnmk appears as the first preferred trunk. When ground is placed on terminal 24 by the operation of plunger 7, a master switch mechanism of sub-group II causes its set of plungers to be moved to position before the second preferred trunk of such sub-group in a man ner similar to that described for sub-group I. The second preferred trunk of sub-group II is multipled to the sub-group I by a conductor 32, the multiples of appearing in sub-group I as fourth choice. This method of slipping the trunk test terminals is carried out through the five groups in a manner readily understood from the foregoing description.

What is claimed is:

1. In a telephone exchange system, a line switch, a main group of calling lines served by said switch, said main group being divided into a plurality of sub-groups, a plurality of trunks common to said main group of lines, means to extend a calling line to a trunk, and means to render certain ones of said common trunks normally accessible as first choices to the lines of a sub-group as preferred trunks, a'different set of preferred trunks being thus assigned to each sub-group.

2. In a telephone exchange system, a line switch, a main group of lines served by said switch, said main group being divided into a plurality of sub-groups, a plurality of trunks common to said main group of lines, there being preferred ones of said common trunks to which the lines of a sub-group normally have access as first choices, there being a different set of preferred trunks assigned to each sub-group, and means for making a preferred trunk accessible to the lines of its sub-group whenever one of such trunks is idle.

3. In a telephone exchange system, a line switch, a main group of lines served by said switch, said main group being divided into a plurality of sub-groups, master switch mechanism individual to each of said subgroups, a plurality of trunks common to said main group of lines, preferred ones of said trunks to which the lines of a subgroup normally have access as first choices,

this trunk means for extending any one of said lines to an idle one of said trunks, contact banks nected to successive banks in such a manner that each sub-group has as first choices trunks appearing in other banks as later choices. I

4. In a telephone exchange system a line switch, a main group of lines served by said switch, said main group being divided into a plurality of sub-groups, master switch mechanism individual to each of said subgroups, a plurality of trunks common to said main group of lines, preferred ones of said trunks to which the lines of a sub-group normally have access as first choices, means for extending any one of said lines to an idle one of said trunks, contact banks for said master switch mechanisms, multiple terminals of said trunks appearing in said banks, said terminals being slipped in groups equal to the number of preferred trunks per sub-group to the successive contact banks, and means for making a preferred trunk accessible to the lines of its sub-group whenever one of such trunks is idle.

5. In a telephone exchange system, a line switch, a main group of lines served by said switch, said main group being divided into a plurality of sub-groups, master switch mechanism individual to each of said subgroups, a plurality of trunks common to said main group of lines, preferred ones of said trunks to which the lines of a subgroup normally have access as first choice, and means including a differentially wound magnet and a relay individual to each of said preferred trunks whereby a master switch mechanism is released and returned to position before one of its preferred trunks as soon as one of such trunks becomes idle.

In witness whereof, I hereunto subscribe my name this 26th day of June, A. D. 1916.

, CHARLES L. GQODRUM. 

